1. Field of the Invention
The present invention relates to a semiconductor device, and in particular, to an electrostatic discharge (ESD) protection device.
2. Description of Related Art
ESD is the main factor of electrical overstress (EOS) which causes damage to most of electronic devices or systems. Such damage can result in the permanent damage of semiconductor devices and computer systems, so that the circuit function of integrated circuits (ICs) is affected and the operation of electronic products is abnormal. Accordingly, a number of methods have been developed to protect the semiconductor IC devices against possible ESD damages. The most common type of ESD protection is the incorporation of a specific hardware inside the IC package. A specially-designed ESD protection device set up between an input pad and an internal device is utmostly required, so as to protect the internal device.
In a deep submicron semiconductor process, the ESD tolerance is getting worse as dimensions of the IC devices are getting miniaturized. Hence, the design for ESD protection has been taken into account when designing ICs. Usually the ESD tolerance for commercially available ICs is required to pass the human body model (HBM) test. In order to sustain the above-mentioned high-voltage ESD test, the large-scaled ESD protection device for ICs is usually applied.